Semiconductor chip packages are used in a variety of devices and conventionally include a package substrate and one or more dies mounted on the package substrate. Semiconductor chip packages sometimes include underfill to provide thermal and mechanical support to the die on the package substrate. For instance, in a conventional design using a flip chip ball grid array die, underfill is applied, as a liquid, between the die and the substrate, thereby filling in the spaces within the ball grid array. The underfill then hardens.
It is not desirable for underfill to flow onto some parts of the package substrate. For example, when underfill flows onto an exposed electrical contact pad, such as a bond finger pad, it can prevent electrical contact with the pad or cause mechanical problems. One conventional solution uses a dam fabricated from solder mask material in an attempt to constrain the flow of the underfill material. A conventional system using a dam also may be supplemented by having exposed electrical contact pads placed up to 200 microns away from the dam thereby creating an amount of clearance for the liquid underfill to traverse should the liquid underfill flow over the dam. Another conventional system uses a trench to slow the flow of underfill. However, it would be desirable to develop more effective techniques to control the flow of underfill material.